Analysis: the raw materials used in nuclear fusion are deuterium and tritium isotopes of hydrogen in seawater, which contains a large number of these raw materials; The substance produced by nuclear fusion is water, which will not pollute the natural environment.
Controlled nuclear fusion has many advantages: (1) The materials it uses are inexhaustible in seawater, and the sources of raw materials are more abundant; (2) The reaction product is water, which will not pollute nature.
So the answer is: the source of raw materials is more abundant, and there is less pollution to the environment.